Continuous resonance trap refractor based assembly

ABSTRACT

A tapered core waveguide which may be configured as a spectral component splitter, a spectral component combiner, and various combinations thereof including a reflective mode of operation. The tapered core waveguide has an aperture and cladding, and is dimensioned such that radiant energy admitted into the core via the aperture and having at least two spectral components would be emitted via the cladding at a location dependent on its frequency and/or its polarization, and that a plurality of spectral components injected to the core via the cladding will be mixed and emitted via the aperture.

RELATED APPLICATIONS

Aspects of the present invention were first disclosed in U.S. PatentApplication 61/701,687 to Andle and Wertsberger, entitled “ContinuousResonant Trap Refractor, Waveguide Based Energy Detectors, EnergyConversion Cells, and Display Panels Using Same”, filed 16 Sep. 2012.Further refinements of the tapered waveguide based Continuous ResonantTrap Refractor (CRTR) and to lateral waveguides with which CRTRs maycooperate, were disclosed together with various practical applicationsthereof in the following additional U.S. Patent Applications 61/713,602,entitled “Image Array Sensor”, filed 14 Oct. 2012; 61/718,181, entitled“Nano-Scale Continuous Resonance Trap Refractor”, filed 24 Oct. 2012;61/723,832, entitled “Pixel Structure Using Tapered Light Waveguides,Displays, Display Panels, and Devices Using Same”, filed 8 Nov. 2012;61/723,773, entitled “Optical Structure for Banknote Authentication”,filed 7 Nov. 2012; Ser. No. 13/726,044 entitled “Pixel Structure UsingTapered Light Waveguides, Displays, Display Panels, and Devices UsingSame”, filed 22 Dec. 2012, now issued as U.S. Pat. No. 8,532,448; Ser.No. 13/685,691 entitled “Pixel structure and Image Array Sensors UsingSame”, filed 26 Nov. 2012, now issued as U.S. Pat. No. 8,530,825; Ser.No. 13/831,575 entitled “Waveguide Based Energy Converters, and energyconversion cells using same” filed Mar. 15, 2013, now issued as U.S.Pat. No. 8,530,825; 61/786,357 titled “Methods of Manufacturing ofContinuous Resonant Trap Structures, Supporting Structures Thereof, andDevices Using Same” filed Mar. 15, 2013, 61/801,619 titled “TaperedWaveguide for Separating and Combining Spectral Components ofElectromagnetic Waves” filed Mar. 15, 2013, U.S. 61/801,431 titled“Continues Resonant Trap Refractors, lateral waveguides, and devicesusing same” filed Mar. 15, 2013, all to Andle and Wertsberger; and61/724,920, entitled “Optical Structure for Banknote Authentication, andOptical Key Arrangement for Activation Signal Responsive to SpecialLight Characteristics”, filed 10 Nov. 2012, to Wertsberger. FurthermorePatent application GB 1222557.9 filed Dec. 14, 2012 claims priority fromU.S. 61/701,687. All of the above-identified patents and patentapplications are hereby incorporated herein by reference in theirentireties.

FIELD OF THE INVENTION

This invention relates generally to waveguide structures, and morespecifically to a tapered core waveguide based combiner and/or splitter,and to combinations and applications thereof.

BACKGROUND OF THE INVENTION

Various areas of physics require spatially separating radiant energyinto its spectral components such as by frequency and/or polarization.By way of example such fields include solar cells, image array sensors,filters, energy harvesting devices, certain types of reflectors, and thelike. Similarly, various areas will benefit from mixing various spectralcomponents into a broader type of radiant energy, combining a pluralityof ‘narrower’ spectral components into a ‘broader’ radiant energy.

In its most basic form, the term ‘refraction’ means the change ofdirection of a ray of light, sound, heat, radio waves, and other formsof wave energy, as it passes from one medium to another. Generally wavesof different frequencies would refract at different angles and thusrefraction tends to spatially separate multispectral radiation into itsspectral components by frequency. The term ‘spectral component’ willrelate to the energy or a portion thereof in the spectral range ofinterest, which is characterized by its frequency, polarization, phase,flux, intensity, incidence, radiosity, energy density, radiance, or acombination thereof. Multi-spectral energy relates to energy having atleast two spectral components.

Electromagnetic (EM) radiant energy extends over a broad frequencyspectrum, however many applications deal only with portions of thisspectrum. Light is one form of radiant energy which may be considered asan alternating EM radiation at very high frequency. Humans perceivedifferent light frequencies as different colors, but there is a largeamount of radiation that is not perceived by humans, generally known asUV (Ultra Violet), and IR (Infra Red), and the term light extendthereto. Visible light ranges generally between 760-300 nm and roughlycorresponds to the peak intensity of solar radiation transmitted throughthe atmosphere. Infrared radiation ranges from the extreme far end oflmm (33 THz; millimeter radio waves) to about 760 nm. The range ofmillimeter waves, also known as Extra High Frequency (EHF), isspecifically considered as part of the possible spectral range ofdifferent embodiments, as their behavior is sufficiently similar for thepurposes of combining and separating radiant energy, so as to benefitfrom various aspects of the invention. As the human eye is capable ofdirectly sensing and differentiating between light of differentfrequencies, it will be used oftentimes to explain the operation ofdifferent aspects of the invention for the sake of brevity and increasedclarity, however the spectral range of interest to which those examplesrelate may be larger, and depends on the application at hand. Withchanges in dimensions, materials and the like, the principle describedherein extend to any electromagnetic radiant energy and thus the all orportions of the spectrum ranging from the EHF to UV should be consideredequivalent, unless otherwise specified or clear from the context.

It is seen therefore that radiant energy extends over a very broadradiation spectrum, and many applications would need to cover onlyportions of this spectrum. By way of example, for solar energyapplications the spectral range of interest will likely be a spectrumcontaining most if not all of the solar spectrum available at thelocation where the solar cell is to be deployed, or the portion thereofwhich is economically used by the device at hand, typically ofwavelength within 2-3 μm to 300 nm for example. The spectral range ofinterest for most display devices will fall within the visible lightspectrum, even if some special application demand extending the spectralrange. In some applications a specific wavelength may be desirablyattenuated, such as by way of example reduction of blue light for pilotrelated devices. Yet, for devices directed to heat energy recovery, itis likely that only the infra-red portion of the spectral range is ofinterest. Similarly, the spectral range of interest may be applicable toportions of a device, such that by way of example, a device may bedirected to a broad spectrum, but portions thereof may be directed to anarrower spectrum, and the spectral range of interest is thus limited tothe range of interest for that portion of the device. By way of anon-limiting example a television may occupy a display portion thatutilizes CRTR's as described below and additional emissions such asaudio outputs. The spectral range of interest of the display may onlyextend to the visible range, even if the device as a whole includes theaural range as well, the aural range does not fall within the spectralrange of the CRTR used in the television. It is seen therefore that theapplication at hand determines the spectral range of interest, and thata spectral range of interest may differ by application, an apparatus, ora portion thereof. Regarding lateral waveguides, which is describedbelow, each waveguide may have its own spectrum of interest, which maydiffer from the spectral range of interest of an adjacent waveguide.Similarly, for array of CRTRs, each CRTR may have its own spectral rangeor ranges of interest.

Therefore, the spectral range of interest is defined herein as relatingto any portion or portions of the total available spectrum offrequencies and/or polarizations, which is being utilized by theapplication, apparatus, and/or portion thereof, at hand, and which isdesired to be filtered, channeled, detected, emitted, and/or reflectedutilizing the technologies, apparatuses, and/or methods of theinvention(s) described herein, or their equivalents.

At sufficiently high frequencies, radiant energy is also commonlyconsidered as a flow of photons, which are quantized units of energywhich increases with frequency. Under this quantum physics description,the energy density associated with electric and magnetic fields areprobability distributions of photons. Therefore certain terms that arecommon to simple electromagnetic energy can be better clarified asrelating to the spectrum of interest. Thus, a dielectric material in theabove mentioned energy spectrum of interest relates to a material havinglow conductivity, and having a band-gap between a filled valence bandand an empty conduction band exceeding the energy of any photon in thespectrum of interest to a specific application. In contrast, atransparent conductor is a material having a finite but meaningfulconductivity due to a partially filled conduction band or partiallyempty valence band but having a band-gap between the valence band andconduction band exceeding the energy of any photon in the spectrum ofinterest. These materials act like a dielectric at high frequencies butact like a conductor at low frequencies. Transparent dielectricmaterials also have low optical losses such that photons efficientlytransmit through such material, at least at the spectrum of interest ora significant portion thereof.

While transparent conductors may be considered as wide bandgapsemiconducting materials, they are used as conductors in mostapplications. Dielectrics, transparent conductors, and semiconductors,as used in these specifications, refer to materials that have adielectric constant at optical frequencies; however the distinctionbetween a semiconductor and the remaining materials is that the bandgapof a semiconductor is not substantially larger than the photon energy.As a general and non-limiting guideline, table 1 describes severalcharacteristics of the different conductive, insulating, andsemi-conductive materials.

TABLE 1 Transparent Semi- Material Metal conductor conductor DielectricBandgap → 0 >>photon ≤photon >>photon DC Conductivity high good Varies →0 Optical Property reflective transparent absorptive transparentDielectric constant complex low loss lossy low loss

Waveguides are a known structure for trapping and guidingelectromagnetic energy along a predetermined path. An efficientwaveguide may be formed by locating a layer of dielectric orsemiconducting material between cladding layers on opposite sidesthereof, or surrounding it. The cladding may comprise dielectricmaterial or conductors, commonly metal. Waveguides have a cutofffrequency, which is dictated by the wave propagation velocity in thewaveguide materials, and the waveguide width. As the frequency of theenergy propagating in the waveguide approaches the cutoff frequency Fc,the energy propagation speed along the waveguide is slowed down. Theenergy propagation of a wave along a waveguide may be considered ashaving an angle relative to cladding. This angle is determined by therelationship between the wavelength of the wave and the waveguide widthin the dimension in which the wave is being guided. If the width of thewaveguide equals one half of the wave wavelength, the wave reachesresonance, and the energy propagation along the waveguide propagationaxis stops.

In these specifications, the term cladding penetration state relates toa condition where energy confined by the tapered core waveguide leavesthe waveguide via the cladding. Generally each waveguide has somenegligible penetration of energy into the cladding, however claddingpenetration state occurs when a significant amount of energy istransported through the cladding. Cladding penetration state isgenerally frequency related, and energy of one frequency may reachcladding penetration state at a different set of conditions than thecladding penetration state of another frequency. By way of non-limitingexample, if 66% of the energy of frequencies between F1 and F2 will exita hypothetical waveguide via the cladding at a distance between 1 um to2 um from the waveguide aperture, the cladding penetration state forF1-F2 would exist between 1-2 um from the aperture. Other frequenciesmay or may not overlap such range partially or completely. Notably thenumber 66% has been arbitrarily selected by way of example only, and maybe modified as an engineering choice according to the application athand.

In these specifications, cladding penetration state is used primarily todefine a location or a region where cladding penetration would occur,rather than necessarily the actual occurrence of cladding penetration.As discussed below, energy may be coupled into the waveguide core viathe cladding at the region about which cladding penetration state wouldoccur, as well as be outputted therefrom.

Stationary resonance condition is a condition in a waveguide where thelocal cutoff frequency of the waveguide equals the frequency of a waveguided by the waveguide, such that the guided wave reflects repeatedlybetween opposing surfaces of the guide, however the correspondingcomponent of energy velocity along the waveguide propagation axis iszero. As the wave frequency approaches the local cutoff frequency of thewaveguide, a sharp decrease in the wave propagation (group) velocity isnoticed at the immediate vicinity of the cutoff dimension, as may beseen by way of example in the lower graph of FIG. 3. While completestationary resonance condition is seldom if ever achievable, for thepurpose of these specifications a stationary resonance (SRC) conditionwill be considered a situation where the guided wave is sufficientlyclose to the complete stationary resonance condition to significantlylower than the speed of light in the bulk material of the waveguide.Stated differently, when a wave falls within the zone of the sharpdecrease in velocity it is considered to be in SRC.

With proper selection of cladding material and dimensions, energy willreach a cladding penetration state and depart the waveguide through thecladding at this stationary resonant condition. This mechanism isrelated to by the acronym CPS-SRC. CPS-SRC often occurs with reflectivecladding, comprising thin metallic cladding. Notably a metallic claddingof lower thickness than the penetration depth to which the cladding islocally exposed would allow energy to pass therethrough and suchcladding may be utilized. Furthermore, when certain metals are disposedat low thicknesses they tend to “ball-up” and form small “islands”. Such“balled-up” metal, and/or intentionally perforated metal cladding mayalso form a discontinuous metal film cladding in a reflective CRTRwaveguide.

Total internal reflection (TIR) is a phenomenon which occurs when aguided wave hits the boundary between the core and the cladding below acertain angle relative to the local propagation axis of the waveguide.The angle is known as the critical angel of total Internal Reflection.When a guided wave reaches or exceeds the critical angle it departs thewaveguide via the cladding under normal refraction. Slightly below thiscritical angle the internal reflection by a finite cladding becomesincomplete in a process known as Frustrated Total internal Reflection(FTIR). This condition occurs mostly with dielectric cladding, butmetallic claddings with small perforations or with thicknesses at ornear the tunnel distance also have angle dependent reflectioncoefficients, resulting in a situation analogous to FTIR. Claddingpenetration condition reached by a wave exceeding the critical angle oftotal internal reflection is referred to hereinafter as CPS-FTIR. BothCPS-FTIR and CPS-SRC are characterized by energy traversing thecladding, thus CPS, or ‘cladding penetration state’ will be usedinterchangeably to denote CPS occurring through any mechanism.

Collectively, objects, materials, and structures, which inter-convertelectromagnetic and electrical energy are known by various names whichdenote equivalent structures, such as converters, transducers,absorbers, detectors, sensors, and the like. To increase clarity, suchstructures will be referred to hereinunder as ‘transducers’. By way ofnon-limiting examples, the term “transducer” relates to light sources,light emitters, light modulators, light sensors, photovoltaic materialsincluding organic and inorganic transducers, quantum dots, CCD and CMOSstructures, LEDs, OLEDs, LCDs, laser sources, receiving and/ortransmitting antennas and/or rectennas, phototransistors photodiodes,diodes, electroluminescent devices, fluorescent devices, gas dischargedevices, electrochemical transducers, and the like. Certain transducersmay be configured to convert energy forms bidirectioanlly, such as asingle transducer which may operate as a converter from electricalenergy to radiant energy, and vice versa. Alternatively transducers maybe built to convert only from one energy form to another. Transducersfor conversion of radiant energy to electricity or electrical signals(hereinafter “LE”), or conversion of electrical signals into radiantenergy such as light (hereinafter “EL”) are known.

A transducer of special construction is the RL type transducer, which isa reflective transducer. Reflective transducers controllably reflectradiant energy. Such transducers may comprise micro-mirrors, lightgates, Liquid Crystals (LCD), and the like, positioned to selectivelyblock the passage of radiant energy, and reflect it into a predeterminedpath, which is often but not always, the general direction the energyarrived from. Certain arrangements of semiconductor and magneticarrangements may act as RL transducers by virtue of imparting changes inpropagation direction of the radiant energy, and thus magnetic forces orelectrical fields may bend a radiant frequency beam to the point that ineffect, it may be considered as reflected. RL transducers may be fixed,or may be used to modulate the energy direction over time. Passivetransducers such as LCD and micromirrors fall into the RL class oftransducers when used to reflect incoming energy, but when used inconjunction with at least one light source, such transducers may also beconsidered as LE type transducers.

Radiant energy transducers, and especially LE transducers, typicallyemploy normal incidence of radiant electromagnetic energy onto aconversion structure. Normal incidence has the limitation of a finiteprobability of detecting energy before it is transmitted through theconversion layer. Energy transmitted through the conversion layer is, atbest, lost and, at worst, converted to heat in the supporting substrate.Several attempts has been made to provide transducers that use ‘sideillumination’ in which the light is inserted from the side of thejunction. Such examples include, inter-alia, in U.S. Pat. No. 3,422,527to Gault, U.S. Pat. No. 3,433,677 to Robinson, and U.S. Pat. No.4,332,973 to Sater.

Prisms and other refractive devices can be used to improve incidenceangles, and to direct different frequencies of radiant energy todifferent regions of a transducer, where each region is optimized for atarget frequency. U.S. Pat. No. 7,888,589 to Mastromattteo and U.S. Pat.No. 8,188,366 to Hecht, disclose examples of such devices. Differentarrangements of concentrators are also known, which are operative toconcentrate energy to transducers. U.S. Pat. No. 5,578,140 to Yogev etal. as well as Hecht provide examples to such arrangements. Thosemethods require significantly increased device area, and reduce thetotal energy per unit area (and per unit manufacturing cost) in exchangefor increased efficiency.

Vertical optical waveguides are known in the prior art. U.S. Pat. No.4,251,679 to Zwan depicts a plurality of transducing cavities having aninwardly inclined wall to receive impinging radiation. Two potentialbarrier strips each having different conduction electron densities; eachpotential barrier strip is connected to a conductor having a preselectedconduction electron density whereby radiation impinging on a cavity willinduce current flow which will be rectified across the potentialbarriers. U.S. Pat. No. 3,310,439 to Seney relates to embedding spaceddimensioned crystals into p-n semiconductor layers of a solar celldevice. The crystals function as waveguides into the photovoltaic layer.

Tapered waveguide directed at trapping radiant energy, as opposed toemitting energy via the cladding, have been disclosed by Min Seok Jangand Harry Atwater in “Plasmionic Rainbow Trapping Structures for Lightlocalization and Spectrum Splitting” (Physical Review Letters, RPL 107,207401 (2011), 11 Nov. 2011, American Physical Society©). The article“Visible-band dispersion by a tapered air-core Bragg waveguide”, (B.Drobot, A. Melnyk, M. Zhang, T. W. Allen, and R. G. DeCorby, 8 Oct.2012/Vol. 20, No. 21/OPTICS EXPRESS 23906, ©2012 Optical Society ofAmerica_“Visible-band dispersion by a tapered air-core Bragg waveguide”B. Drobot, A. Melnyk, M. Zhang, T. W. Allen, and R. G. DeCorby, 8 Oct.2012/Vol. 20, No. 21/OPTICS EXPRESS 23906, ©2012 Optical Society ofAmerica) describes out-coupling of visible band light from a taperedhollow waveguide with TiO2/SiO2 Bragg mirrors. The mirrors exhibit anomnidirectional band for TE-polarized modes in the ˜490 to 570 nmwavelength range, resulting in near-vertical radiation at mode cutoffpositions. Since cutoff is wavelength-dependent, white light isspatially dispersed by the taper. These tapers can potentially form thebasis for compact micro-spectrometers in lab-on-a-chip and optofluidicmicro-systems. Notably, Bragg mirrors are very frequency selective,complex to manufacture, and require at least a width higher than ¾wavelength to provide any breadth of spectrum. In addition to the verynarrow band, the Bragg mirrors dictate a narrow bandwidth with specificpolarization, while providing however a fine spectral resolution.

However the known art does not provide a multi purpose small scalesplitter/combiner/reflector of radiant energy. There is therefore aclear and heretofore unmet need for a small-scale spectral manipulationstructure that would do one or more of: split multispectralelectromagnetic radiation to obtain spectral component(s) contained inthe multispectral radiation; mix spectral components to obtainmultispectral electromagnetic radiation; redirect incomingelectromagnetic energy so as to be diverted at some nonzero angle fromits initial propagation direction; separate electromagnetic componentsby polarization; combine electromagnetic components of differentpolarizations, controllably reflect certain spectral components, and anycombination of the above.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a taperedwaveguide for separating mixed electromagnetic waves into spectralcomponent(s) and/or for combining spectral components into mixedmultispectral electromagnetic energy.

It is a further object of the present invention to provide a refractorwhich is easily manufactured, and which refracts energy into spatiallyseparated component frequencies and/or polarizations. It is anotherobject of the present invention to provide a refractor that will steerthe incoming energy from the incidence direction or acceptance cone andradiate the spatially separated energy at various locations and/orangles from the incidence direction of the waveguide.

It is a further object of the invention to provide a compact opticalmixer/combiner that will combine radiant energy components from aplurality of sources at various locations and/or angles from the normalincidence direction of the waveguide, and output the combined radiationfrom a single aperture.

It is yet a further object of the invention to provide a hybridstructure in which energy incident at the aperture in one portion of thespectrum is collected while energy generated about the taperedwaveguide, in another portion of the spectrum is combined and radiatedout of the structure.

It is yet another object of the invention to provide selectiveabsorption and/or reflection of portions of an incoming spectrum ofradiant energy, so as to provide passive reflection of lights asrequired for a passive display device. Alternatively, the structure mayabsorb energy of one or more portions of the spectrum, reducingreflection of such energy.

In very basic terms, the present invention relates to a structure calledContinuous Resonant Trap Refractor (CRTR) which is based on a waveguidehaving a tapered core, the core having a wide base face forming anaperture, and a narrower tip. The core is surrounded at least partiallyby a cladding. The CRTR may be operated in splitter mode, in combinermode, and/or in reflective mode. In splitter mode the radiant energywave travels along the depth direction extending between the apertureand the tip, and in mixer, or combiner mode, the wave travels towardsthe aperture. The depth increases from the aperture towards the tip,such that larger depth implies greater distance from the aperture. Dueto the core taper, when multi-frequency radiant energy is admittedthrough the CRTR aperture, lower frequency waves will reach claddingpenetration state before higher frequency waves, and will penetrate thecladding and exit the waveguide at a shallower depth than at least onehigher frequency wave. Thus, the CRTR will provide spatially separatedspectrum along its cladding. Conversely, when operated in combiner mode,a wave coupled to the core via the cladding at coupling depth, willtravel from the emission depth towards the aperture, and differentfrequencies coupled through the cladding will be mixed and emittedthrough the aperture. Coupling radiant energy into the CRTR core fromthe cladding, will be related as ‘injecting’ or ‘inserting’ energy intothe CRTR.

Certain non-symmetrical or multi-faceted symmetrical tapered core formswill cause separation of the aperture-admitted radiant energy to bepolarization sensitive. Thus, by way of example, a square pyramid orfrustum CRTR core will separate incoming radiant energy into itscomponent polarizations as well as by its frequency. This behavior willbe reversed when the CRTR operates in mixer/combiner mode, such thatenergy emitted from the aperture will reflect the polarity created byseparate sources, and injected into the CRTR at different faces. By wayof none-limiting example, if light source A injects modulated energyinto one face of a square cross-section pyramidal core, and light sourceB injects differently modulated energy into a perpendicular face ofcore, the light emitted by the aperture at the base of the pyramid willhave one spectral component at a first polarization reflecting themodulation of source A, and a second spectral component at 90° to thefirst spectral component, representing the modulation of source B. Thusthe two sources A and B form an angle therebetween, the angle is said tobe parallel to a width plane when an angle exists between the twosources when their location is projected to at least one width plane,regardless of their actual depth.

In a first aspect of the invention, there is provided a spectralsplitter for spatially separating multispectral radiant energy into atleast two spectral component thereof, the splitter comprising a taperedwaveguide core having a first end and a second end, the first enddefining an aperture, the core having a depth direction extendingbetween the first end and the second end, wherein the depth magnitudeincreases with distance from the first end towards the second end. Thecore also has a width dimension in at least one direction substantiallytransverse to the depth direction, the core width monotonicallydecreasing in magnitude in at least one direction, as a function of thedepth such that the width magnitude at the aperture is higher than thewidth magnitude at the second end. A cladding is disposed at leastpartially around the core. The first end of the core, i.e. the aperture,is dimensioned to allow passage of radiant energy comprising at least afirst and a second spectral components each having a frequencyassociated therewith, wherein the first spectral component has a lowerfrequency than the second spectral component. The varying width of thecore resulting in the first and the second spectral components eachreaching a state (CPS) at which they will penetrate the cladding and beemitted from the waveguide via the cladding at a respective first andsecond depth, wherein the first depth is less than the second depth.

The skilled in the art will recognize that the tapered waveguide coreand the cladding disposed at least partially thereabout form awaveguide, and due to the core being tapered, spectral components havinglower frequency will reach a CPS prior to spectral components havinghigher frequency. The core or the cladding may comprise fluid.

The width of a two dimensional CRTR is transverse to the depthdirection, while for a three dimensional CRTR, at any depth the CRTR hasa plurality of width transverse to the depth direction. The differentwidths for a single depth form a width plane, which is transverse to thedepth direction, and the term ‘in at least one direction’ as related towidth, relate to directions on the width plane or parallel thereto. Anygiven depth correspond with its width plane, and thus there are infinitenumber of parallel width planes.

In certain embodiments the tapered core may exhibit a generally roundcross-section on its width plane, however a perfect circle is notrequired. In some embodiments the tapered core cross-section may besymmetrical and in others asymmetrical. In certain embodiments the crosssection is square, hexagonal, octagonal, or other symmetricalmultifaceted shape. In some embodiments the core may form an elongatedwedge, i.e. forming a plurality of rectangular cross-sections on therespective width planes.

In a similar fashion when operated in splitter mode, and withmultifaceted core, the first and second spectral components may differfrom each other by having different polarization, rather than, or incombination with, different frequency. Therefore, in a second aspect ofthe invention, there is provided a spectral splitter for spatiallyseparating multi-polarization radiant energy into at least two spectralcomponent thereof, the splitter comprising a tapered waveguide corehaving a first end and a second end, the first end defining an aperture,the core having a depth direction extending between the first end andthe second end, wherein the depth magnitude increases with distance fromthe first end towards the second end. The core also has a plurality ofstacked cross-sections in a respective plurality of width planes, thecross-sections having at least one width dimension decreasing inmagnitude as a function of the depth such that the width magnitude atthe aperture is higher than the width magnitude at the second end, atleast one of the cross-sections being either a multifaceted symmetricalshape, or an asymmetrical shape. A cladding is disposed at leastpartially around the core. The first end of the core, i.e. the aperture,is dimensioned to allow passage of radiant energy comprising at least afirst and a second spectral components each having a differentpolarization associated therewith, The shape of the cross-section of thecore resulting in the first and the second spectral components eachreaching a state at which they will penetrate the cladding and exit thewaveguide via the cladding, at a first and second direction,respectively. At least in cores having symmetrical multifacetedcross-section, if the spectral components have differing frequencies aswell as different polarization, they will reach their CPS at differentdepth as well as be emitted at a different direction.

Optionally, the splitter also comprises at least a first and a secondenergy transducers for converting radiant energy to electrical energy(LE) and/or electrical energy to radiant energy (EL), wherein the firsttransducer is disposed in a path to receive the first spectralcomponent, and the second transducer is disposed in a path to receivethe second spectral component, after the respective spectral componentsexists the waveguide. The splitter or the combiner may be embedded in astratum. A stratum is a surrounding structure about CRTR's

In a third aspect of the invention there is provided a spectral combinercomprising a tapered waveguide core having a first end and a second end,the first end defining an aperture, the core having a depth directionextending between the first end and the second end, wherein the depthmagnitude increases with distance from the first end towards the secondend, the core having a width dimension in at least one directiontransverse to the depth direction, and the core width decreasing inmagnitude in at least one direction, as a function of the depth suchthat the width magnitude at the aperture is higher than the widthmagnitude at the second end. A cladding is disposed at least partiallyaround the core. At least a first and a second radiant energy sourcesare disposed about the cladding such that when energized they coupleenergy emitted therefrom to the core via the cladding. The energyemitted from the energy sources is coupled into the core at or about thecladding penetration depth of at least one wave in the energy emitted bythe energy source. Stated differently the energy will couple to the coreat a depth where the core width is at, or adjacent to, an integermultiple of half of the respective wavelength of the source. Preferablythe integer multiple is one, and the core width is slightly larger thanhalf the wavelength to provide efficient coupling of the energy into thecore.

The term “about the cladding” or equivalently about the CRTR or itscore, should be construed to mean being coupled to via energy path,which implies that the transducer is disposed about the cladding notonly by being physically adjacent to the cladding, but also when anenergy path such as beam propagation, waveguide, and the like, existsbetween the location where energy is transferred in or out of thecladding, and the transducer. Similarly, the disposition about thecladding is set by the location at which the energy exists or enters thecladding. Thus, by way of example if the transducer is coupled to thecladding via a waveguide such that the energy couples at depth A of theCRTR, the transducer is considered to be disposed at depth A regardlessof its physical location relative to the RCTR.

The depth at which the wave injected via the cladding would couple intothe tapered core presents a challenge to define. At the exact depth ofCPS the wave may not couple properly into the core, thus expressionssuch ‘slightly above CPS depth’, ‘adjacent to’ ‘about’, and others, asreferred to the coupling of light into the tapered core incombiner/mixer mode should thus be construed as the depth at whichenergy injected into tapered core via the cladding would best couple tothe core to be emitted via the aperture. The parameters of selecting thebest coupling fall within considerations such as manufacturelimitations, required precision, cost, engineering choices, and thelike. Such depth would generally be referred to as “coupling depth”

The skilled in the art may recognize a similarity between the waveguideformed by the tapered core and the cladding of the different aspects ofthe invention described thus far. Furthermore, the aspect of theinvention which required a specific symmetrical multifaceted corecross-section in at least one depth, may act as a core for other aspectsof the invention. Indeed the tapered core waveguide disclosed may beoperated in a splitter mode and/or combiner mode, depending on thedirection of energy propagation. In splitter mode energy admitted intothe waveguide via the aperture is split to its spectral componentseither by frequency, polarization, or a combination thereof, and thespectral components are emitted via the cladding. When operated in acombiner mode, spectral components of the energy are admitted into thewaveguide via the cladding and the spectral components are combined andare emitted via the aperture. Notably, the tapered core waveguide may beoperated as combiner and a splitter simultaneously, for differentspectral components. As certain structural aspects are common to the twoaspects on the invention, many of the following additional features maybe considered applicable to different aspects, separately or incombination. For the purpose of this disclosure, negligible material andinterface loses in the CRTR are ignored.

In combiner embodiments where the energy sources are of differentfrequency, they are arranged to couple to the core at different widthplanes, and optionally energy sources are arranged to inject energywhich will be emitted via the aperture at separately controlledpolarization. The energy sources would be arranged to inject the energyat different axes of the cross-section of the core, thus forming anangle therebetween on a plane parallel to a width plane. Clearly,combinations of energy sources to produce combinations ofmulti-frequency and multi-polarization are explicitly considered. Inorder to derive multiple polarizations, a multifaceted core ispreferred, wherein the first and the second energy sources are disposedto couple the energy emitted therefrom into different facets of themultifaceted core.

CRTRs may also be operated in reflective modes, where a RL transducer isdisposed such that a spectral component of radiant energy admitted intothe tapered core is emitted via the cladding, and impinge upon the RLtype transducer. The RL transducer controllably reflects at least aportion of the energy impinging thereupon via the cladding back into thecore, where it is emitted via the aperture.

In splitter mode, asymmetrical core cross-section or multifacetedsymmetrical cross-section would also provide a splitter that will splitthe energy admitted into the core via the aperture to spectralcomponents based on their polarization. Splitting the aperture-admittedenergy in combinations of frequency and polarization are yet anotherfeature of the invention.

To increase brevity, the structures described above, whether operated incombiner mode, splitter mode, reflective mode or any combinationthereof, will be related as CRTR. CRTRs are described more completelybelow.

Most commonly, CRTRs are disposed within a surrounding structure whichwill be referred to in these specifications as “stratum”. The outercladding of the CRTR may be disposed, at least in part, within astratum. The stratum may be disposed on top of a substrate if one isused. Additional materials may be disposed on top of the stratum, suchas anti-reflective layers, protective layers, collimation layers,lenses, and the like. Stratums may be roughly divided into slab stratumand layered stratum, and the selection of the type of stratum is amatter of technical choice. Certain layered stratums are formed as aplurality of superposed waveguides, termed stacked waveguides, orequivalently as lateral waveguides hereinafter. The waveguides in such astacked waveguide system may be coupled with one or more CRTR taperedwaveguides such that spectral component(s) separated by a CRTR aredirected toward one or more of the stacked waveguides. In otherembodiments the stratum comprises a slab of material that istransmissive of the radiant energy spectral range of interest.

In some embodiments the tapered core is a symmetrical multifaceted core,and a first transducer is disposed about a first face of themultifaceted core, and a second transducer is disposed about a secondface of the multifaceted core. In splitter modes the energy transducersconvert radiant energy to electrical energy (LE transducers) and thestructure provides detection of spectral components of two separatepolarizations. In combiner modes, the transducers convert electricalenergy to radiant energy (EL transducers), or modulate radiant energy inaccordance with an electrical signal (RL transducers), and the structureprovides a combiner which can emit radiant energy through the aperturewhere the energy has two separately controlled polarization spectralcomponents, each reflective of the respective signal fed to thetransducers.

The cladding may comprise metal having a thickness in the order of, orlower than, the skin penetration depth for at least one spectralcomponent, at or about the cladding penetration depth of the spectralcomponent. In some embodiments the cladding comprises a continuous or adiscontinuous metal film, and some embodiments the cladding comprises amaterial having a lower refractive index than the refractive index ofthe core. Such cladding will often be dielectric.

Generally, and especially in metal cladding devices, the local thicknessof the cladding does not exceed the local skin penetration depth. Insome embodiments the local thickness of the cladding does not exceed aquarter of the wavelength associated with the first spectral component.In some embodiments the local thickness of the cladding as a whole doesnot exceed a quarter of the local wavelength. Claddings of more thanhalf the local wavelength are workable. Cladding of higher thickness,such as cladding of more than three quarters of the local wavelength aregenerally undesirable, unless at the tip of the waveguide where theirinfluence is negligible. However in the case of straight pit walls,paralleling generally the depth direction, thicker cladding may beplaced between the pit and the core, to ease manufacturing.

In some embodiments the cladding thickness is reduced as a function ofdepth, such that the cladding becomes thinner with increased depth.However in some embodiments the cladding becomes thicker as a functionof depth. Oftentimes in these embodiments the core and cladding aredisposed in a pit having a straight wall, and the core is inserted intothe cladding. In pit based CRTR as described above, the cladding may bethicker than a whole wavelength at the tip end of the tapered core.

In certain embodiments the splitter further comprises a plurality ofcontrollable light modulators, disposed about the cladding.

While the CRTR is useful as a standalone invention in certainapplications, it is oftentimes more useful when a plurality of such CRTRstructures operates in combination. To that end there is provided anarray comprising a plurality of spectral splitters. In some embodiments,such array further comprises one or more lenses disposed over theapertures of the plurality of splitters. In some embodiments theapertures of the plurality of splitters lie substantially on a focalplane of the lens. Optionally, the lens comprises a mating surface formating with the plurality of apertures, the mating surface having aplurality of protrusions extending therefrom, at least one of theprotrusions dimensioned to act as the cores of a corresponding spectralsplitter. In such embodiments, a plurality of pits is formed in astratum, and the protrusions on the lens are aligned with matching pits,and the stratum and the lens are mated. Cladding may be deposited in thepits and displaced by the protrusions, may be deposited on theprotrusions prior to mating, or may be flowed into the pits after themating. The cladding may be a fluid, and may or may not be solidifiedafter the stratum and the lens are mated. Each of the members of thearray may then become a pixel in an image sensor, or a portion of anadvanced, concentrated solar cell, phased array antenna, and the like.

Similarly, CRTRs operated as combiners may be operated as an arrayforming a display in the visible light spectrum, or be operated as anantenna which may act as a phased array antenna. As described, a singleCRTR may operate in a combiner mode and/or in splitter mode, andtherefore a combination of the functions described above may beutilized. By way of non-limiting example, a singletransmitting/receiving antenna may be formed of an array of cooperatingCRTRs. Such array may act to steer a beam in any of desired directionsby feeding the transducers of the CRTRs with signals having a phasedifference therebetween.

Phased array antennas operate on principles of interference between theradiant energy emitted from various antenna elements. Such interferencemay be created by manipulating the phase and/or amplitude of the signalemitted form a plurality of antenna elements. The steering of theantenna offers the ability to radiate extremely narrow beam which incertain embodiments may be utilized for writing or marking very smallfeatures such as features used in the photolithography. the small sizeof the individual CRTRs and their ability to provide high intensitysignals make the CRTR based phased array a powerful tool. By way ofexample, an array of CRTRs dimensioned to operate at the UV range wouldbe very small at just over half of the longest emitted wavelength. Inthis type of lasers only a single transducer may be used per CRTR,however a plurality of transducers may provide better resolution. UVlasers coupled to separate CRTRs or to one CRTR, may be individuallycontrolled and fed different phase and/or amplitude signals, and theirinterference would allow for a beam to form features that are farsmaller than the wavelength. Such arrays may also be used for writing ofcertain images, for ablating material in a programmatic manner, as wellas form scanning beams such as radar and the like.

The terms ‘symmetrically multifaceted core’ or ‘multifaceted symmetricalcore’ imply that the core is shaped as three dimensional multifacetedbody having at least one symmetrical polygonal cross-section. Theconsecutive cross-sections of such body may differ in shape, butgenerally are smaller in at least one dimension, the further thecross-section is along the depth axis. In some embodiments, the base isof different shape and slowly vary towards the symmetrical polygon.However relating to a radiant energy having at least a first spectralcomponent having a first polarization and a second spectral componenthaving a different polarization, a symmetrical multifaceted core may berecognized by having at least one cross-section at the width plane,where in splitter mode, the first spectral component will exit thecladding in different direction than the second spectral component.Commonly, the multifaceted symmetrical core is formed by a polyhedronhaving a symmetrical polygonal base and converging triangular ortrapezoidal sides, where the base is substantially transverse to thedepth direction. Notably multi-faceted core symmetry and certainasymmetrical core forms may operate to separate or combine spectralcomponents of different polarization. For the purposes of thesespecifications, such asymmetrical core forms is considered asmultifaceted symmetrical form, and the specifications and claims extendthereto.

A CRTR is considered to operate in hybrid mode when energy is bothadmitted and emitted via the aperture. In certain embodiment this modeinvolves energy being admitted via the aperture and at least portionsthereof being emitted via the cladding, while other energy is beinginjected via the cladding and emitted via the aperture. In otherembodiments a portion of the energy admitted via the aperture isselectively reflected back therethrough, such as when utilizing a RLtype transducer. A hybrid transmitter may be considered as any one of a)an emitting CRTR operating as a mixer, b) a sensing or receiving CRTRacting in splitter mode, and/or c) a reflective CRTR operating with atleast one RL type transducer for controllably reflecting at least partof energy admitted via the aperture. Thus, by way of example, a call fora splitter CRTR in these specifications may be fulfilled by a hybridCRTR capable of acting as a splitter.

CRTRs may also operate in reflective mode, by providing light gateswhich will reflect radiant energy back into the CRTR tapered core. Alight gate disposed at the depth where radiant energy is emitted out ofthe cladding, will cause the emitted energy to be reflected back intothe cladding, and thence emitted via the aperture. An array of CRTRs inconjunction with RL transducers which act as light-gates will havevariable reflectivity such that at least a portion of the light incidenton the array at the associated frequency will be reflected, inaccordance with the setting of the light gate reflectors. The term lightgate should be construed to a device able of controlling light passageor block, absorption, reflectance, and the like, across a spectral rangeof interest, which may extend beyond the visible range. The spectralrange of interest is dictated by the application at hand. The broad bandcapabilities of the CRTR allows modulation of its reflectance over abroad band of frequencies, extending the ability for reflectance intothe UV, IR, and even the mm wave spectrum. Reflective mode may alsooperate in polarization sensitive mode as explained above for EL and LEtransducers in polarization sensitive mode.

Therefore, in certain embodiments there is provided a hybrid spectralsplitter and combiner the hybrid comprising: a tapered waveguide corehaving a first end and a second end, the first end defining an aperture,the core having a depth direction extending between the first end andthe second end, wherein the depth magnitude increases with distance fromthe first end towards the second end; the core having a width dimensionin at least one direction transverse to the depth direction; the corewidth decreasing in magnitude in at least one direction, as a functionof the depth such that the width magnitude at the aperture is higherthan the width magnitude at the second end. A cladding disposed at leastpartially around the core, wherein the first end of the core isdimensioned to allow passage of radiant energy comprising at least anadmitted spectral component having a frequency associated therewith,wherein the varying width of the core resulting in the admitted spectralcomponents reaching a CPS—a state at which they will penetrate thecladding and exit the waveguide via the cladding—at a at a frequencydependent depth. At least one energy transducer is disposed about thecladding to receive the spectral component. Furthermore, the hybridcomprises at least a one radiant energy source disposed about thecladding to couple energy emitted therefrom to the core via thecladding, wherein the energy emitted from the energy source is coupledinto the core about the coupling depth. Optionally, the transducers andthe light sources are integrated in a single component. Furtheroptionally the hybrid and/or the light sources and/or the transducersmay be embedded in a stratum. Importantly, embedded in the stratum doesnot necessitate that the whole CRTR will be completely enveloped by thestratum, but merely that the stratum and the CRTRs are in communicationfor transferring energy therebetween, or a portion of the CRTR isdisposed in contact with the stratum.

An additional aspect of the invention provides a reflectivemicrostructure comprising a tapered waveguide core having a first endand a second end, the first end defining an aperture, the core having adepth direction extending between the first end and the second end,wherein the depth magnitude increases with distance from the first endtowards the second end, the core having a width dimension in at leastone direction transverse to the depth direction, the core widthdecreasing in magnitude in at least one direction, as a function of thedepth such that the width magnitude at the aperture is higher than thewidth magnitude at the second end. A cladding disposed at leastpartially around the core, wherein the first end of the core isdimensioned to allow passage of radiant energy comprising at least oneadmitted spectral component having a frequency associated therewith. Thevarying width of the core results in the spectral component reaching acladding penetration state at which it will penetrate the cladding andexit the waveguide via the cladding, at a frequency dependent depth. AnRL type transducer is disposed about the cladding, in a path tocontrollably reflect the admitted spectral components which was emittedvia the cladding, and reflect at least a portion the radiant energy ofthe spectral component via the cladding into the core, where it will beemitted through the aperture.

CRTRs may be two dimensional or three dimensional, and the claims relateto both types.

Further combinations of elements of different aspects of the inventionwould be clear in light of the teachings of these specifications.

SHORT DESCRIPTION OF DRAWINGS

The summary above, and the following detailed description will be betterunderstood in view of the enclosed drawings which depict details ofpreferred embodiments. It should however be noted that the invention isnot limited to the precise arrangement shown in the drawings and thatthe drawings are provided merely as examples.

FIGS. 1a and 1b respectively depict two-dimensional simplifiedwaveguides.

FIG. 2 depicts a simplified diagram of equivalent plane wavespropagating within a waveguide being identical to a waveguide mode.

FIG. 3 depicts the wavenumber as a function of frequency, the ray angleas a function of frequency, and the energy velocity as a function offrequency for two modes of a waveguide. Imaginary wavenumbers belowcutoff frequency are not shown.

FIG. 4 depicts a cutout of a simplified Continuous Resonant TrapRefractor (CRTR).

FIG. 5 shows a cutout of a CRTR embedded in a stratum comprising lateralwaveguides.

FIG. 5a depicts an embodiment with a bulk material stratum.

FIG. 6 depicts a cross-section of a CRTR array 900 with several optionalconstruction details.

FIG. 7 depicts a CRTR acting as a combiner, in combination with optionaloptical switches.

FIGS. 8a-8e provide different examples of polarization sensitive CRTRs

FIG. 9 depicts simplified graph showing angle-dependent transmissivitythrough a dielectric cladding

FIG. 10 depicts a portion of a CRTR based array antenna.

FIG. 10A depicts a cross-section of a CRTR tapered core, having a centervoid or pole.

FIGS. 11 A-D depict an optional method of manufacturing.

FIG. 12 depicts a device where CRTR's cores are created as part of astamp/cover.

DETAILED DESCRIPTION

Certain figures and embodiments of the invention will be describedherein by way of example to increase the understanding of differentaspects of the invention.

FIGS. 1a and 1 b alternately depict a short region of waveguide withinsignificant variation of thickness, and are provided for simpleexplanation of the propagation characteristics of radiant energy withinsuch waveguides. For the purpose of explanation, FIGS. 1a and 1 b may beconsidered to represent a cutout of a short region of a CRTR taperedcore waveguide, or a cutout of a waveguide within lateral waveguides.

FIG. 1.a shows a two dimensional waveguide 100 comprising a waveguidecore material 101 of thickness (width), h, formed between conductors 102and 103. Optionally, the waveguide core material 101 could be replacedby a plurality of layers forming an aggregate optically equivalent to auniform material having dielectric constant, ε, and the same overallthickness. Such construction would be recognized as equivalent by theskilled artisan.

The core may be considered to have an average relative dielectricconstant, E, determined using formula well known in the art andresulting in a speed of electromagnetic plane wave propagation in thebulk of the core material, V_(b)=300*10⁶/√{square root over (ε)} metersper second. It is noted that √{square root over (ε)} is the refractiveindex (commonly denoted as ‘k’ in semiconductor manufacture field, andas ‘n’ in the field of optics). In the depicted example, bounding layers102, 103 are conductors, providing mirror reflection.

The cutoff frequency, F_(CN), of the Nth order mode is obtained as

F _(CN) =NV _(B)/2h wherein N is the mode order

Below this cutoff frequency an electromagnetic wave cannot travellaterally along the waveguide X axis. At the critical frequency, aguided plane wave reflects repeatedly between the upper and lowerconductors but makes no lateral progress along the waveguide. Above thecutoff frequency a wave travels with a dispersion equation

$\beta_{N} = {2\pi\sqrt{\left( {F^{2} - F_{CN}^{2}} \right)}}$

Wherein βN is wavenumber of the Nth order mode, F being the wavefrequency, and FCN is the cutoff frequency as described above.

The wave has N half-wavelengths of variation across the thickness, h,and propagates with a wavelength along the guide λGN=2π/βN.

Higher order modes have larger values of N and have higher cutofffrequencies for the same thickness waveguide. An incident plane wave 110at a low angle of incidence will couple best to the most uniformwaveguide mode 111, so the fundamental mode is most readily coupled forincidence parallel to the waveguide.

Radiant energy incident at an angle, θi 112, will be partially refracted113 into the guide and partially reflected. The fraction of an incidentwave admitted into the guide is determined by the integral of theincident wave front 110 with the mode shape 111. Narrow guides comparedto the wavelength have a broader angular acceptance range, operatecloser to their resonant condition, and have slower energy velocities.

FIG. 1.b shows a similar two dimensional waveguide based waveguide 150comprising a dielectric material 151 of thickness, h, formed betweendielectric cladding materials 152 and 153. Notably, transparentconductors will act in a similar fashion, and their use is alsocontemplated.

The critical frequency, FCN, is obtained as

F _(CN) =NV _(B)/2(h+δ _(N)),

where δN (depicted schematically as the dimensions indicated by 162 and163 at FIG. 1b ) represents the effect of partial penetration of modeprofile 161 into the neighboring dielectric regions, and h representsthe thickness (width) of the core region. It is seen therefore thatwhile the width at which a CPS occurs may differ, the qualitativeproperties are similar to those of the conductor clad waveguide basedtransducers. We note that if δN is comparable to the cladding layerthickness, FTIR energy leakage will occur and the waveguide will have afinite propagation loss. This may or may not be desirable depending onthe mechanism employed for causing energy to penetrate the cladding.

FIG. 2 depicts a waveguide 200 with extents along y of ±h/2 andpropagation along x. The waveguide supports a fundamental mode withcross-section amplitude distribution 201 and propagation wave along thewaveguide with a frequency-dependent period 202. The wave may be writtenas

$A_{({X,Y})} = {{{COS}\left( {\pi\frac{y}{h}} \right)}*{\exp\left( {{j\;\beta_{N}X} - {j\; 2\pi\;{Ft}}} \right)}}$

The cosine is ½ the sum of two exponentials, representing upward 203 anddownward 204 plane waves. The waves make an angle 205 with respect tothe propagation direction 206, given as

$\theta = {\cot^{- 1}\sqrt{\left( {\frac{F^{2}}{F_{C}^{2}} - 1} \right)}}$

such that as frequency, F, approaches the cutoff frequency, FC, theangle approaches 90°.

FIG. 3 plots the wavenumbers, β1 301 and β2 302, having cutofffrequencies, FC1 and FC2 respectively, for a respective first and secondmode of a waveguide of thickness, h, and dielectric constant, ε. Thefrequency axis 307 is logarithmic and normalized to cutoff frequencyFC1. In the middle graph of FIG. 3, the angle of the equivalent planewaves from parallel are also shown for the first 303 and second 304modes respectively. The angle of the equivalent plane waves fromparallel is also shown for the first 303 and second 304 modes, thecritical angle ° C. for total internal reflection 313 and thecorresponding ratio of the critical frequency compared to cutoff for thefirst 314 and second 315 modes being shown for a dielectric-cladwaveguide. In the bottom graph of FIG. 3 the energy (or group) velocity,VE1 305 and VE2 306 are shown normalized to the bulk speed of light inthe material, VB. As shown, the respective group velocity is zero at thecutoff frequencies and then rapidly approach VB at high frequencies. Thearea where the group velocity slows significantly relative to VB iseasily distinguished.

A wave at high frequency relative to the waveguide's cutoff frequencywill travel effectively at the speed of light in the bulk material VB,with a very low angle relative to the propagation axis of the waveguide.Such a wave has a very shallow angle of incidence on the boundaries ofthe waveguide and is said to have grazing incidence. By way of example,a wave having a frequency about six times the cutoff frequency has anangle of incidence of about 10° and travels at effectively the speed oflight in the waveguide core material.

While the examples provided in FIGS. 1a, 1b , and 2 were provided usingtwo dimensional waveguide, extension of the above to a three dimensionalwaveguide of finite extent in z is well known in the art and similarexpressions for the cutoff frequencies and dispersion relationships willbe clear to the skilled in the art in light of the presentspecifications.

Having considered the idealized waveguide shown with constant width atFIGS. 1a, 1b , and 2, attention is now given to the effect of taperingin a CRTR having a tapered waveguide core.

As described above, a CRTR may be operated in one of two fundamentalmodes generally referred to as a ‘splitter mode’ and a ‘combiner mode’,and further in hybrid and reflective modes. The more detailedexplanation will first concentrate on the splitter mode.

FIG. 4 depicts a cutout of a simplified Continuous Resonant TrapRefractor (CRTR) which is a waveguide having a tapered core 73 and acladding 710, and dimensioned as described below. In splitter mode theCRTR allows a wave in the spectral range of interest to propagate in thecore until it reaches a cladding penetration state at a frequencydependent width, which is also a frequency dependent depth due to thecore taper. The core and cladding are selected to allow the wave topropagate in the waveguide and to depart the waveguide via the cladding.The tapered core 73 has a wide end denoted in FIG. 4 as h_(max) definingan aperture, and a narrow end h_(min) referred to as a tip. The core issurrounded at least partially by cladding walls 710, which areconductive or have a lower refractive index than the refractive index ofthe core. The core region may comprise a single region or a plurality ofdielectric regions, and in some embodiments a fluid is utilized as thecore material. It is noted that the cladding may extend only partiallyabout the core, but the portion which is considered as the waveguide isthe portion of the core bounded by cladding at least in two opposingsides of one width direction.

At any depth, the core 73 has a corresponding plurality of widthdimension(s) transverse to the depth dimensions, the width dimensionsfor a given depth defining a width plane transverse to the depthdimension. The width plane dissects the tapered core to form a twodimensional cross-section. Stated differently, the width being anydirection lying in plane transverse to the depth directions, i.e. aplane that is penetrated by the depth dimension and is substantiallyperpendicular thereto. The core cross-sections may be of any geometryand form, and may be symmetrical or asymmetrical. By way of example,h_(max) and h_(min) and Ft denote width extending on both sides of thedepth dimension X-X, and each is on a different width plane. Notably,while those examples denote symmetry about the at least two sides of thedepth axis, such symmetry is not required, and other width dimensions onthe respective planes may or may not be of varying magnitude. However,by virtue of the taper, considering at least two width planes, the planecloser to the aperture will have at least one width dimension having alarger magnitude than at least one width dimension magnitude on theplane that is closer to the tip. While in the example depicted in FIG. 4the cross-sections are received from a pyramid or a cone with theclipped apex, any desired shape may be selected as long as the widthdirection is reduced as a function of depth. In the depicted example,the taper forms angle 760 from the vertical.

Electromagnetic radiant energy admitted via the aperture propagates inthe core generally along the depth dimension X-X The tapered corewaveguide guides waves from the aperture, generally along the depthdimension X-X extending from the aperture h_(max) towards the tiph_(min). The depth being an axis which extends indefinitely, and inthese specifications increases from the aperture towards the tip, suchthat larger depth implies greater distance from the aperture.

The electromagnetic radiant energy waves admitted via the aperturepropagate along the depth dimension until such waves reach a plane ofsufficiently constricted cross-section, to cause the wave to reach acladding penetration state. The width of the CRTR core which causes theCPS for a wave of a given frequency is termed the ‘emission width’ forthat wave. The distance of an emission width for a specific wave fromthe aperture, when measured along the depth direction, is referred to as‘emission depth’.

The core width is dimensioned such that when multi-frequency energy isadmitted through the aperture and propagates along the core depth, itwill cause a lower-frequency spectral component to reach a claddingpenetration state at a first depth, and the core will further taper to awidth that will cause energy of a higher-frequency spectral component toreach a cladding penetration state at a second depth, the second depthbeing larger than the first depth.

Therefore, for a given CRTR spectral range of interest S_(i), rangingbetween λ_(max) to λ_(min) which represent respectively the longest andshortest wavelengths of the spectral range of interest as measured inthe core material, wherein λ′ is at least one wavelength in S_(i), thedimensions of a frequency splitting CRTR taper are bounded such that

a. the aperture size ψ must exceed the size of one half of λ_(max);b. the CRTR core size must also be reduced at least in one dimension, toat least a size ζ which is smaller than or equal to one half ofwavelength λ′.

Thus the CRTR dimensions must meet at least the boundary of

{ζ≤λ′/2<λ_(max)/2≤ψ} where the CRTR sizes defined above relate to a sizein at least one dimension in a plane normal to the depth dimension. InFIG. 4 the aperture size ψ=h_(max). It is noted however that not allwaves in S_(i) must meet the condition b. above. By way of example,certain waves having shorter wavelengths than h_(min)/2 may fall outsidethe operating range of the CRTR. Such waves which enter the CRTR willeither be emitted through the tip, reflected back through the aperture,or absorbed by some lose mechanism.

Notably if a third spectral component λ″ is present, and has a higherfrequency than λ′, it may be emitted at greater depth than λ′ or beemitted via the tip if the tip is constructed to pass a spectralcomponent of frequency λ″, or it may reflected or absorbed.

The CRTR aperture is dimensioned, when operating in splitter mode, toallow the entry of a spectral component having at least the lowestfrequency in the spectral range of interest, which means that thelongest wavelength in the spectral range of interest for the CRTR isdefined by the aperture width in at least one dimension. Notably, thespectral range of interest may be limited by other considerations toshorter wavelengths. The core taper in at least one dimension which mustencompass both the emission width of the longest wave in the spectralrange of interest as well as an emission width of at least one shorterwavelength within the spectral range of interest. The CRTR either willtaper to less than the emission width of the shortest wave in thespectral range of interest or will allow the final portion of thespectral range of interest to exit vertically at a truncated tip of thecore. Larger widths than those emission widths at the inlet aperture, orsmaller widths than those emission widths at the tip, are allowed.

If the tip is truncated or otherwise allows passage of at least some ofthe spectral components that were admitted by the aperture, the highestfrequency in the spectral range of interest for the CRTR is defined bythe longest wavelength that will be emitted via the cladding. If the tipdoes not allow energy to pass therethrough, the highest frequency in thespectral range of interest for the CRTR is the highest frequency to beemitted via the cladding, and detected or reflected by any desiredmanner.

The spectral range of interest for a CRTR operated in mixer mode is therange between the highest and lowest frequencies of radiant energyinjected into the tapered core via the cladding. In hybrid andreflective modes of operation the spectral range of interest for theCRTR is a combination of the above ranges, as dictated by theapplication at hand. Notably, all of those spectral ranges of interestare defined for the CRTR. Portions of the CRTR or other elements of theinvention may have different ranges of interest.

The cladding penetration mode of the CRTR may be CPS-FTIR, or CPS-SRC,or a combination thereof.

As described above, waveguides have a cutoff frequency, which isdictated by the wavelength in the waveguide materials, and the waveguidewidth. As the frequency of the energy propagating in the waveguideapproaches the cutoff frequency Fc, the energy propagation speed alongthe depth of waveguide is slowed down. The energy propagation of a wavemay be considered as having a depth dependent varying angle θ relativeto the propagation direction, and thus also relative to the cladding,until a CPS is reached.

If the cladding walls are comparable in width, w, to the skinpenetration depth, δ, then energy will transfer across the claddingthrough frustrated total internal reflection (FTIR) with a transmittedpower fraction proportional to exp(−2w/δ).

Similarly, if metal cladding is used, and the metal cladding is on theorder of the skin penetration depth, δ, which is determined by theresistivity, ρ, radian frequency, ω=2πF, and permeability, μ, as

${\delta = \sqrt{\frac{2\rho}{{\omega\mu}\;}}},$

then energy will also partially transmit through the metal cladding inproportion to exp(−2w/δ).

While operating in splitter mode, refraction by the CRTR occurs in suchfashion that spectral components exit the cladding along its side. Evenfor metal-clad waveguides in which the cladding penetration state may insome cases be reached near the stationary resonance condition,refraction is seldom or never perfectly perpendicular to the waveguideaxis. This angle will in most cases be closer to 90° in conductor cladwaveguide and further from 90° in dielectric cladding. The angle may becomputed utilizing the refractive indices of the core material, thecladding, and any surrounding medium, by simulation, or may simply bedetermined empirically.

Energy 730 in the spectral range of interest is incident on thewaveguide at its aperture, at an angle which permits energy admission.Waves having a lower frequency than the cutoff frequency F_(min) arereflected 735. Waves 740 having frequency higher than F_(max) exitthrough the tip of the tapered waveguide if an exit exists. Waves havinga frequency between F_(min) and F_(max) will reach their emission width,and thus their cladding penetration state, at some distance from theaperture of the waveguide depending on their frequency, as shownschematically by arrows 750 and 752.

In general terms then, when multi-frequency radiant energy is admittedthrough the CRTR aperture, lower-frequency waves will reach theiremission depth before higher-frequency waves, due to their longerwavelength and the taper of the core. As the wave energy departs theCRTR at its emission depth, lower-frequency wave would penetrate thecladding and exit closer to the aperture than higher-frequency wave.Thus, the CRTR will provide spatially separated spectral componentsalong its cladding, while at the same time refracting the spatiallyseparated energy away from the depth axis of the CRTR.

Examining the behavior of a wave of arbitrary frequency F_(t), whereF_(min)<F_(t)<F_(max), which enters into the waveguide at its apertureat an incidence angle nominally parallel to the propagation axis X-X,the angle θ between the wave and X-X will vary as the wave propagatesalong the X-X axis due to the narrowing of the waveguide and increase ofthe cutoff frequency, as depicted schematically by F_(t). As the waveapproaches emission depth X(F_(t)) where either the tapered waveguidecutoff frequency equals or nearly equals F_(t), or the angle θapproaches the critical angle θc, the wave cannot propagate any furtherwithin the CRTR core. The wave F_(t) is thus either radiated through thecladding of the waveguide or is trapped in resonance at depth X(F_(t)).Considering a perfectly reflective cladding, fora continuum of waves ofdifferent frequencies F_(min)<F1, F2, . . . F_(x)<F_(max), admitted viathe aperture of the tapered waveguide 71, the waveguide becomes acontinuous resonant trap, in which without cladding penetration thewaves of different frequencies become standing waves, trapped atresonance in accordance to their frequency along the X-X axis. Suchtrapped waves however are either leaked through the cladding by thefinite probability of “tunneling” though the cladding or are lost toabsorption in the waveguide. If the cladding may be penetrated, thetapered core waveguide becomes a continuous resonant trap refractor(CRTR), as the waves are also refracted from the depth axis. Thisrefraction allows directing specific spectral components of the incomingspectrum to predetermined target zones and provides special separatingof the spectrum.

The skilled in the art would also recognize that while this simplifiedexplanation describes waves entering the CRTR in parallel orientation tothe X-X axis, the operation will be similar on waves having any angle ofincidence which is admittable by the waveguide construction.

The tip may be open in the sense that it does not hinder passage of someradiation therethrough, or closed in the sense that it blocks at least aportion of the spectral range of interest. In embodiments where the tipdoes not taper to a point, energy 740 may be allowed to exit the tip endof the CRTR, or a mirror may be formed at the tip, to reflect unwantedenergy back through the aperture.

FIG. 5 shows a cutout of a stratum 503 in which a CRTR 71 is embedded.The stratum in this example comprises lateral waveguides—a plurality ofstacked waveguides 550 a-e, into which the energy entering the apertureh_(max) is coupled in a frequency sorted fashion. The figure depicts asimplified path of a wave 504 incident onto a tapered waveguide core 501and refracted into a waveguide mode. The waveguide mode is generallyillustrated by rays 505, 506, and 507 of ever larger angle relative tothe waveguide boundary. In the case of a dielectric clad waveguide,there exists a critical angle beyond which total internal reflectionwill not occur and the wave is refracted instead of reflected. At alocation along the waveguide where the width is slightly larger thanthat resulting in a SRC, the ray angle will exceed the critical anglefor total internal reflection and will instead be refracted 508 in thecladding 710. Stated differently, the ray will reach its emission widthand thus its cladding penetration state. For dielectric clad CRTR, theratio of the core and cladding dielectric constants determines thecritical angle above which total internal reflection cannot occur. Belowthis angle, and therefore above a critical frequency, there is a finitepenetration, δ into the cladding. Note that δ increase with decreasingfrequency. At a critical emission depth, above the cutoff frequency, thecritical angle for total internal reflection is reached and the wavewill no longer be guided and therefore exits the CRTR before the cutofffrequency depth. If the structural material of waveguide 550 e has anindex of refraction higher than that of the cladding, then the ray willrefract again, becoming trapped in judiciously located lateral waveguide550 e, and will propagate 509 in that waveguide. The ratio of thecladding and transducer dielectric constants determines the angle ofemission, which will always be directed downward slightly fromperpendicular for a cladding having lower refractive index than that ofthe core.

Spectral components of lower frequencies will exit in a similar mannerat a wider point in the tapered waveguide 501, being directed to earlierlateral waveguides such as 550 a-d, and higher frequency spectralcomponents will exit deeper into the tapered reflector (not shown).

The energy may be directed to transducers which may be detectors fordetection of different frequencies, to absorbers for harvestingelectrical energy, to RL type transducers, or to any combinationthereof. If a specific frequency is reflected back into the CRTR core bya RL transducer or even a simple fixed reflector, it will be emitted viathe aperture. In the case of combiners, the lateral waveguide may havelight sources embedded therein. The transducers may be housed within thestratum or outside thereof. FIG. 5a depicts an embodiment where thestratum 2012 comprises bulk material in which the sorted energypropagates. In the depicted embodiment, the CRTRs 2008 and 2009 separateincoming light into Red, Green and Blue (RGB) primary colors, and thosecolors are detected respectively by transducers 2002, 2003, and 2004 forCRTR 2008, and transducers 2005, 2006, and 2007 for CRTR 2009, Thetransducers are shown in a substrate 1200. While this is one alternativeconstruction, the transducers may be located in the stratum, and/or inlateral waveguides, and the selection of the location of the transducersis a matter of technical choice.

As noted, CRTR use may extend to the millimeter wave range (EHF), oreven to the microwave range. Depending on where between cm waves andmicron IR the range of dielectric constants available increasesdramatically. By way of example, water has an index of refraction ofnearly 10 at radio frequencies but only 1.5 at IR to UV. There arenumerous optical materials with low and high index at mm wavefrequencies and below. Thus while the principles of operation of CRTRsare similar, the materials and sizes differ. A millimeter/microwaveoperated CRTR is a channelized filter integrated into a horn antennawherein the channelized ports are lateral to the horn and the in-lineexit port is a high pass filtered output for a broad band input. Suchdevice may be utilized as a an excellent front end for amultiplexer/diplexer, and as a general purpose antenna that hasexcellent noise figure and improved anti-jamming as thosecharacteristics are determined at the front en of devices which usethem.

FIG. 6 depicts a cross-section of a CRTR array 900 with several optionalconstruction details. An optional lens 980 may be disposed on top of theCRTR or on top of high pass filter 901. In certain embodiments, the highpass filter is incorporated into the lens. Use of a lens can modify theangle of acceptance of CRTR. The apertures of CRTRs 902, 903, and 904are contiguous or nearly contiguous at the inlet surface, providingeffectively complete collection of incident radiant energy. By makingthe apertures 960 of the CRTRs wider than the critical width at thelowest frequency of interest, F_(MIN), 961 all desired frequencies areaccepted into the waveguides. A tradeoff exists where the wider theaperture, the narrower the acceptance angular range for any givenfrequency of light. Managing that tradeoff is an implementationdependent engineering choice. As the refractors taper, there existsspace therebetween 963 for transducers 911, 912, 913. FIG. 6 furtherpresents two optional features, namely the stepped taper present in thecore of CRTR 903, and an optional excess handler 931, at the tip of CRTR902. Radiant energy having higher frequency than a desired range may behandled by an excess handler 931. Excess handler 931 may be a reflectorwhich reflects energy of shorter wavelengths than the energy that wasrefracted through the cladding back towards the aperture, and the energyis reflected from the CRTR. Alternately the excess handler 931 may be ahigh energy transducer located at the CRTR tip to convert all of theenergy that was not refracted. Use of an excess handler is advantageousto reduce heat buildup, and other ill effects of such energy, or formaximizing the energy recovery of the device. Thus, by way of example ifthe CRTR is designed to receive light from the IR range to the purple,UV energy which enters the CRTR is reflected by a reflector that acts asan excess handler 931, and is re-radiated outside the aperture,preventing damage to UV sensitive materials within the CRTR or itssurrounding media.

CRTRs may be manufactured by a variety of methods, and are generallyembedded in a stratum in most cases. The stratum may form a singlematerial which allows radiant energy of the spectrum of interest topropagate therethrough, or may contain a plurality of transducersarranged in layers such that each transducer is positioned to receiveits own spectral component from the CRTR. A common way comprisesproviding the desired stratum, and forming pits therein by processessuch as ion milling, reactive ion etch, focused ion beam, and the like,the cladding material is then deposited into the pits, and the core isformed thereabove. In another exemplary manufacture, the CRTRs areformed by providing a substrate, forming pits therein, flowing claddingmaterial and providing a ‘stamp’ which is an object that has CRTR coresprotruding therefrom. The stamp may be removable or form a portion of adevice once manufacture is complete. In certain embodiments, the pitsare tapered, and in certain embodiments the pits have vertical walls,which simplifies manufacturing. Cladding material may be disposed on thelens/stamp, or may be present in the pits prior to alignment and mating.In some cases the cladding may be a fluid which may or may not besolidified at a later stage. The stamp may be removed in certainembodiments, but may also form a portion of the resulting device, suchas forming a lens, a high pass filter, a sealant portion, a mount andthe like.

In the case of conductive cladding material the dielectric constant ofthe core material 606 is arbitrary. However if the stratum compriseslateral waveguides which may be shorted by the cladding, a dielectricintermediate material is needed.

It is noted that light emitters disposed about the cladding are able tocouple waves into the CRTR at frequency selective locations, resultingin light emitted at the aperture of the CRTR being the combination oflight inserted along the CRTR. Thus the CRTR becomes a linear opticalmixer or combiner (the terms mixer and combiner being usedinterchangeably). While light is utilized in the following example, thespectrum of interest may cover any portion of the spectrum.

FIG. 7 depicts a CRTR acting as a combiner, in combination with optionaloptical switches. Radiant energy sources 142, 147, 149, are each ofdifferent frequency, which by way of example would be considered to bered, green and blue, respectively. The radiant energy sources aredisposed such that their emission will be inserted to the tapered coreadjacent to, or at, the cladding penetration depth for their respectivefrequency to provide good coupling into the CRTR, or stated differently,at their coupling depth. Alternatively the coupling depth may be set fora higher order mode of the wave being coupled. As the radiant energy ispresented beyond the critical angle of the cladding, it will penetratethe cladding, the energy will be admitted into the core and will bemixed with other injected spectral components. The combinedmulti-spectral radiant energy 141 will be emitted from the aperture ofthe CRTR, after accounting to losses within the structure.

Stated differently, energy emitted from energy sources whose output isto be mixed, would follow a path via an intermediate material such asthe lateral waveguide core, buffers, and/or other material, to thecladding, and thru the cladding to the CRTR core. For best coupling ofthe energy to the core, the coupling depth will be about the fundamentalhalf wavelength of the frequency being injected.

Optionally, light modulators 144R, 144G, and 144B, such as liquidcrystal material, switchable mirrors, and the like, are provided tomodulate light entering the CRTR. Optionally, in an array of CRTRs, useof such optical switches will allow usage of a single light source 142,147, 149 to provide controlled light to a plurality of CRTRs.

The choice of the number of light sources and waveguides is not limitedto three or to the specific colors in this example. White light may beused, obtaining similar results by relying upon the filtering inherentin coupling to the CRTR, and the white light would act instead of, or inaddition to, one or more individual light sources 142, 147, 149. Thesame principle of operation may be utilized to combine other portions ofthe spectrum, such as MWIR, LWIR, EHF, and the like.

In some embodiments, light modulators 142, 147, and 149 act ascontrollable reflectors, namely a RL transducer, and are disposed aboutthe CRTR and selectively reflect at least a portion of the lightrefracted from the CRTR core, back to into the CRTR core. In the exampledepicted in FIG. 7, The light reflected into the core will be emittedback out via the aperture. The resulting reflective pixel will thusre-radiate a selectable portion of the original aperture-emittedspectrum, to provide an outputted light of a desired color, while theenergy not reflected will be absorbed into the stratum, or otherwisedirected away from the aperture. By reflecting light of the primarycolors at varying proportions back into the CRTR core, a wide range ofperceived colors may be outputted from the aperture. Such structureprovides a pixel operating passively from incoming light and utilizingmerely the power required to maintain the RL transducers at a desiredstate. By way of example, such reflecting light modulators may becreated from liquid crystals which require very low energy, frommicro-mirrors, by way of example, but piezoelectric, piezomagnetic, andcertain semiconductor combinations may be utilized. An array of CRTRbased pixels combined with RL transducers will form a passive,“true-color” display panel, optionally with different colors and atdifferent polarizations. Arrays

of passive pixels utilizing reflected light may be utilized to form verylow power display panel, similar to those colloquially known as “digitalink” or E ink” displays.

If energy transducers are placed in combination with light sources orreflectors along a CRTR's depth direction, the combination may beutilized for a combined power harvesting device and a display. Thus, byway of example, if 144R, 144G, and 144B are controllable reflectors orlight sources located at emission depths of red, green, and blue colorsrespectively, energy harvesting transducers 146 and 148 may be disposedat emission depths differing from those primary colors, and the energyharvested therefrom may be utilized to power light sources orrefractors, and their adjoining driving circuitry. Panels containing aplurality of CRTRs embedded in supporting material containing energyharvesting transducers in combination with reflectors or light sourceswill provide a self energizing panel which may be used for self poweringdigital ink displays, an active light emitting panel, or a panel withlarge grain color change, such as covering panels for structures,vehicles, and the like.

Circular CRTR apertures offer polarization independent emission from theCRTR, where the polarization depends only on the radiant energy admittedvia the aperture. In combiner mode energy emitted from the aperture willbe polarization neutral, and in a CRTR operating in splitter mode,energy will be emitted from the CRTR periphery will be polarizationneutral. However, CRTR tapered cores do not require geometricalsymmetry, nor a constant width about the depth axis. If desired,cross-sections such as elliptical, rectangular, and other geometries maybe used to provide a CRTR with polarized response, if such is desired.

The devices shown in FIGS. 8a , -8 e permit individual detection orcontrol with respect to a plurality of energy polarizations.

FIG. 8a depicts a CRTR with elliptical core cross-section in a widthplane, by way of example of but one possible asymmetrical CRTR 2020.Radiant energy of polarization Ey would enter the CRTR aperture 2030,and would exit the CRTR and impinge on a surface or a transducers group2045, while light entering the CRTR with polarization Ez would impingeon the surface or a transducers group 2040 at a different depth. It isnoted that the elliptical shape is not mandatory and other elongatedshapes are also considered.

FIGS. 8b-8d represent a simple example of a multifaceted symmetricalCRTR core. Using multifaceted core such as square, hexagonal, octagonalshapes and the like provide multi-polarization separation. FIG. 8brepresent an elevation and 8 c represents a perspective view of one CRTRhaving a square core 1050, and transducers 1052 and 1057 which willdetect energy at respective 90° polarization to each other. While 8 bdepicts transducers for a single frequency but with differingpolarization, FIG. 8c shows the combination of frequency andpolarization detection or mixing. While the CRTR 1050 operates insplitter mode, radiant energy 1055 is admitted to the CRTR core 1050 viathe aperture and travels along the depth direction towards the tip. Theenergy is divided between the different transducers groups 1052 (R, G,and B), 1054 (R, G, and B), such that each transducer receives aspectral component separated by polarization as well as by frequency.Thus by way of example, the pair 1052 r and 1054 r would each receive aspectral component of a red frequency, but of differing polarization,and similarly transducers 1052 g and 1054 g would receive a spectralcomponent of a green frequency but with differing polarization, andtransducers 1052 b and 1054 b will have the same with blue frequency.Clearly, if desired a single frequency band may be detected by includingonly a pair of transducers, or polarization only may be detected for awider range of frequencies by directing the multi-frequency spectralcomponents emitted from varying depths into a single transducer for eachpolarization.

Asymmetrical tapered core cross-sections operate similar to multifacetedcores, where energy is sorted by polarization according to the shapeaxes. Not every asymmetrical cross-section would result in usablepolarization dependent spectral separation, but generally shapes havinga plurality of axes, and especially shapes having symmetry about atleast one of the axes, while not necessarily about all axes, will tendto exhibit polarization selectivity. However for brevity it is assumedthat when ‘multi-faceted symmetry’ core is used, unless clear form thecontext, the term extends to include asymmetrical core shapes thatfunction to provide polarization selectivity.

As the CRTR was shown to act symmetrically in splitter mode, the samearrangement would act to mix spectral components of narrow band energysources, into a broader, multi-frequency radiant energy, where thenarrower spectrum sources would be directed towards the core and couplethereto at an angle projected on the width plane. In combiner mode,energy is inserted to the CRTR through the cladding and is outputted viathe aperture. Thus if the units marked transducers 1052 and 1054 (R, G,and B, respectively) represent a plurality of light source at differentangular locations about the depth dimension of the CRTR, it would resultin polarized light corresponding to the location and frequency of thelight sources being emitted from the aperture. An exemplary top view isprovided in FIG. 8e , where light sources 1072 and 1074 are disposedabout the CRTR at 90° relative angle, which will result in individuallycontrolled horizontal and vertical polarized light emitted from the CRTRaperture. It is noted that additional energy sources may be disposed onthe opposite sides of the CRTR. The depicted round shape of the CRTR isrepresentative of any desired core shape.

The skilled in the art would readily recognize that a hexagon wouldprovide light polarized at 120° as depicted by hexagonal CRTR 1060,where each of the transducer pairs 1062, 1064, and 1066 detects incomingenergy polarized at 120° respectively. Similarly, octagonal CRTR wouldprovide 45° relative polarization separation, and the like. It is notedthat even if the core is formed into such cross-section at only aportion of its depth, the polarization of the polarized light or aportion thereof would be so filtered into the various components due tothe physics of cladding penetration and waveguide resonance anddetection of a plurality of polarization is thus enabled.

The following is but one example provided to demonstrate designconsiderations for a CRTR. In order to meaningfully discuss dimensionsin a CRTR, first the angle-dependent transmissivity through a dielectricfor a parylene-N cladding (n=1.661) and AIN core (n=2.165) in a stratumwith n=2.2. The critical emission angle is 39.9° and occurs when thefrequency is 1.556 times the resonant trapping frequency.

Three-quarters of the available power at a given frequency willpenetrate the cladding over an angular arc from the −6 dB point to justabove the critical angle. It is desired that the emitted beam be asnarrow as possible and emit over as short a region of CRTR wallscorresponding to the depth direction as possible. A basic span of 2° ofarc is selected in the design example provided herein. In Parylene-Nthis condition is achieved at a thickness of 0.137λo, where λo is thefree space wavelength. Realizing that the wavelength is shortened by1.661 in parylene-N, the thickness normalized to the local wavelength is0.228λ′_(clad). Preferably the thickness would be at least 0.243λo(0.4λ_(clad)) to obtain less than 1° of angular spread. Thisrelationship shows the advantage of having the thickness of the claddingchange as a function of the depth to optimize transmissivity of eachwavelength.

At another extreme, all tolerances are relative to the dimension beingcontrolled. Making a CRTR pit thicker than the target and thenbackfilling with cladding, as is done in some embodiments, results in aCRTR tolerance that is the sum of an error proportional to the pitdiameter plus an error proportional to twice the cladding thickness. Ata thickness of 0.8λ for the cladding there would be twice the error incladding thickness as there would be for the 0.4λ cladding thickness andthe pit error would also be larger. The end result would be excessiveerror in the vertical location of the cladding penetration state. Forthis reason, Bragg gratings, which necessitate at least three layers of0.25λ with alternating index of refraction, are impractical for CRTRcladdings, and cladding thickness below half wavelength, and even belowquarter wavelength is desired while cladding thickness of 0.75wavelength and above is undesirable using current constructiontechnology. In metal cladding, the desired cladding thickness is inorder of the penetration depth.

A phased array antenna is an antenna composed of a plurality ofradiating elements being fed via phase controller which allows changingthe phase between different antennas for transmitting antenna, andmeasuring phase difference between received signals. During transmitoperations, beams are formed by shifting the phase of the signal emittedfrom each radiating element, to provide constructive/destructiveinterference so as to steer the beams in the desired direction. Phasedarrays are common in the radar field, but have applications elsewhere.When mounted on a moving platform phased arrays are often used to formSynthetic Aperture Radar (SAR) which provides high resolution byrepeated ‘illumination’ of a target by pulses and syntheticallycomputing a model of the scanned target.

As CRTRs may be used well into the EHF range, and possibly even forlonger waves, they act as an antenna either for transmission or forreception, as well as for mixing signals. However in the range ofvisible and UV imaging, the ability for fine control of a very narrowbeam of light is utilized in many applications such as semiconductormanufacturing, scanning microscopes, and the like. The added capabilityof the CRTR to control multiple polarizations further assists inproviding finer control of the beam characteristics, including, by wayof example, utilizing interference of differing frequencies anddiffering between different polarizations. Thus the CRTR based phasedarray antenna is useful throughout the range of millimeter waves wellinto the UV range.

CRTRs may be utilized as a general purpose antenna that has excellentnoise figure and improved anti-jamming as those characteristics aredetermined at the front end of receivers. Furthermore, at themicrowave/millimeters wave range material selection is dramaticallyincreased. Most materials have frequency dependent dielectric constant,which is high in the IR, EHF, and microwave range, but this dielectricconstant drops rapidly at the visual and near IR domains. By way ofexample, water has an index of refraction of nearly 10 at radiofrequencies but only 1.5 at IR to UV. There are numerous opticalmaterials with low and high index at millimeter wave frequencies andbelow. Thus while the principles of operation of the CRTR are the sameas for the optical domain, the materials and sizes differ, andmanufacturing is easier. CRTR based phased array antennas offeradvantages, as described above, in many areas such as communications bynarrow beam, designation of a target with visible or invisible light, tophotolithography of nanometer sized features.

FIG. 10 depicts a portion of a larger array operating as a phased arrayantenna. Firstly, separators 77 isolate each CRTR from other CRTRs sothat each CRTR 902, 903, 904, operates as an independent radiatingelement. A transmitting antenna is described, but a receiving antennawill operate similarly if receivers are utilized. Radiating source typeEL transducers 1101, 1102, and 1103 couple energy of a first frequencyvia the cladding into the respective CRTR core. Phase controller 11600controls the relative phase of signals going to the radiating sources,and thus the phase of the signals emitted from each individual CRTR. Asknown, the phase difference causes the beam emitted from the CRTR arrayto have a direction that may be modified by controlling the phasedifference between individual elements. Beam forming and shaping bychanging phase and/or intensity relationship between a plurality oftransmitting elements is well known in phased array antennas.

Optionally radiating source transducers such as 1120, 1121, and 1122couple energy ata second frequency via the cladding into the respectiveCRTR core. As the CRTR is capable of mixing signals of very broad band,the antenna array can be used to send more than one beam and steer thebeams individually. Those beams may be formed sequentially orsimultaneously.

Thus each CRTR and its associated transducers form a versatiletransmitting element, and the array can steer a beam emitted form thatantenna by the phase controller. Notable, when configured for receivingoperation by having LE type transducers coupled to the CRTRs, the phasedarray antenna can provide information regarding the direction ofincoming signals using similar techniques, by observing the phasedifferences and/or intensities, rather than by transmitting. The phasecontroller 11600 therefore is substituted with a signal processor.

The transducers may be of any desired type, and frequency befitting thetask at hand, including laser, EHF, microwave, visible light, UV light,and the like. As stated above, transducers may be placed so as toreceive radiant energy entering the CRTRs, forming a receiving antenna,where the receiving direction is detected by the relative phase ofsignals received from a plurality of CRTRs. While most phased arrayantennas operate best at a specific frequency and its harmonic, thebroad-band nature of the CRTR allows a phased array receiving antenna ofvery broad spectrum. Such antenna is very useful for signal intelligencegathering.

Notably, radiant sources may also a plurality of lasers, which willallow directing a laser beam to a desired direction, at high intensitydue to constructive interference.

A receiving CRTR operating with a plurality of transducers in varyingdepths forms a channelized filter integrated into a horn antenna whereinthe channelized ports are lateral to the horn and the tip exit port is ahigh pass filtered output for a broad band input. Therefore the CRTRacts not merely as a side fed horn antenna, but taking the signal fromeach transducer allows handling of sub-bands separately, reducing noiseand increasing antenna merit. Therefore, there is provided a front endfor electromagnetic radiant energy receiver, comprising at least one,and preferably a plurality of CRTR's having a plurality of transducersarranged to receive differing frequency bands. Each of the transducersof a single CRTR forms a channel of a predetermined frequency band. If aplurality of CRTRs are used in combination, respective members of theplurality of transducers may be coupled together.

FIG. 10A depicts a cross-section of a tapered core 905 for a CRTR,showing an optional center member 906 extending along the depthdimension. The member may comprise a different material than the core,or may form a void. In certain embodiments such member allows anincrease in the core diameter, which eases manufacturing. The member maybe formed prior to creating the core by filling, deposition, materialremoval, and the like.

FIGS. 11A, 11B, and 11C depict a manufacturing method for the CRTRs. Themethod accommodates relatively imprecise etching of the CRTR outerdimensions which is done by any desired method, such as wet etch, plasmaetch, reactive ion etch, “Lithography, Electroplating, and Molding”(Colloquially known as LIGA—Lithographie, Galvanoformung, Abformung),ion milling, laser etch, and the like. A stratum 1012 is deposited oversubstrate 1200. The stratum may be formed with lateral waveguides asshown, or as a slab stratum. Optionally other layers such as protectivecap layer, buffer layers, and the like, are also deposited. The stratumis etched with pits 1275 defining the CRTR outer shapes. The term pitsin this context are the voids in the stratum into which the CRTR's arecreated or placed, including the cladding and the cores.

A stamp 1270 having protrusions 1271 corresponding to the CRTR cores isprovided for insertion into the pits in the stratum, as shown in FIG.11B. In one optional embodiment, a filler dielectric material 1277B isdisposed within the pits, and the stamp is aligned and inserted suchthat the pits and the protrusions are in registration. The claddingmaterial is displaced into the desired shape by the insertion of thestamp.

In other embodiments the stamp protrusions 127 are first covered withdielectric material 1277A. The stamp is then inserted aligned andinserted such that the protrusions and the pits are in registration.

In some embodiments the stamp is aligned and inserted as described, andcladding material is flowed into the pits, filling the spaces betweenthe pits and the stamp. The cladding material may then be cured in placeif desired. Regardless of the placement method, the goal is to place thedielectric material within the pits between the stratum and theprotrusions. Thus the dielectric material 1277A, 1277B, or the flowedmaterial described above, shall all be related to as numeral 1277. FIGS.11B and 11C show the stratum and the stamp after mating.

The dielectric material may comprise a UV curable material, a thermosetpolymer, a self-curing polymer, a glass, a dielectric fluid, optionallyincluding gas or air, and the like. In some embodiments, the dielectricmaterial itself forms the cladding, while in other embodiments it actsonly as an intermediary, or a portion of the cladding. In embodimentswere the dielectric described above is an intermediate material, theprotrusions may be coated with the cladding, which may be made of thinand/or perforated metal, or another dielectric material, and thendielectric material 1277 is disposed as described above.

Optionally, the cladding material comprises a powder and the process isperformed at a temperature in which the powder flows about the stamp.Alternatively, the stamp is heated to melt the powder.

In some embodiments, the dielectric material 1277 planarizes theimprecise formation of the etched pits 1275.

In certain embodiments the stamp, or a portion thereof, is made ofradiant energy transmissive material while in other embodiments thestamp is withdrawn and core materials is deposited at the voids wherethe protrusion existed when the stamp and stratum were mated. Inembodiments where the stamp 1270 is left in the device, it may also beformed to any desired shape to accommodate the intended use of thedevice. Thus the stamp may form structure such as a protective layer,anti-reflective layer, collimation layer having collimators place on topof the CRTR's apertures, concentrators, mirrors, lenses, and the like.When a stamp is left in the device, it may be referred to as a cover, asit provides a cover to the stratum, and optionally also acts as asealant to fluid that may be utilized for the cladding.

This construction allows fora wide variety of techniques and materialsfor depositing the cladding materials. In some embodiments a fluid isused as the cladding, and the stamp acts as a seal, while theprotrusions serve as the CRTR cores. In embodiments where the claddingis UV curable, the UV may be applied via the stamp. Dies and jigs may beused to facilitate the alignment process.

FIG. 11C depicts a cross-section of CRTRs formed after the stamp and thestratum has been mated. However this embodiment depicts certain optionalfeature. First, it depicts the option where for ease of manufacturing,the pits 1275 are formed larger than the size necessitated by the outerdimension of the cladding, if the cladding follows the tapered core.Doing so allows higher manufacturing tolerance as the pits may be madelarger, and in some embodiments may be made vertical, near vertical, or,as commonly happens during etching, have scalloped walls. Furtheroptionally, an intermediate material 1290 may be disposed within thepits. The cladding 1277 may in such embodiment be disposed on the stampprotrusions 1271, which is advantageous for embodiments where thecladding is metallic, but can also be applied to dielectric material.The stamp and stratum are aligned and joined. In some embodiments theintermediate material is hardened after the mating. In certainembodiment the intermediate material is a fluid.

The stamp based embodiment offers several additional options. In oneembodiments, the cladding is made thicker to fill all the space betweenthe core and the pit wall. Such embodiment may require a dipper pit, asthe path of the light refracted from the CRTR core would be angleddownward and will take longer distance to reach the transducer. In suchcase material 1290 would be the actual cladding material. In certainother embodiments the intermediate material may act as an insulator toprevent shorting of the lateral waveguides by a metallic cladding 1280.

FIG. 11D is a detail cross-section of the optional method of creatingCRTRs using a stamp. This example utilizes a slab stratum. A pluralityof transducers 1273 is formed on a substrate 1200. The substrate hasoptional sidewall or walls 1274 which extend above the substrate, and isformed to receive the stamp therein. The optional sidewalls form aretaining wall for cladding material. The stamp 1270 has a plurality ofprotrusions 1271 projecting therefrom, the protrusions being dimensionedas CRTR cores, and will indeed become the CRTR core if the stampmaterial is transparent to the intended radiant energy, and the stampbecomes integral to the device. Cladding material 1277 is disposed onthe substrate, and the stamp is mated with the substrate. When the stampis placed on the substrate, it displaces the cladding material. In anoptional embodiment, the stamp is disposed on top of the substrate, andthe cladding material is flowed into the spaces between the stamp andsubstrate. In both methods, the cladding material may be hardened or itmay be a fluid. The optional side walls 1274 serve to hold fluidcladding material if used, to facilitate alignment of the stamp, and insome embodiment form a seal to prevent escape of cladding material. Byutilizing this method the CRTR is formed in a slab type stratum, whichis created by the cladding material 1277. The transducers 1273 aredisposed about each core, to receive radiant energy emanatingtherefrome. If the cladding material is hardenable, as described forembodiments above, the side walls may not be required after thehardening. In such construction the sidewalls may be separate from thestructure as a whole. The skilled in the art would recognize that thecladding material may be applied to the stamp rather than the substrate,and that the side walls, if utilized, may be applied to the stamp aswell.

Core materials and cladding materials may comprise a plurality ofmaterials as desired to change the refractive index or other lightpropagation and guiding characteristics of the structure as a whole. Byway of non-limiting example, the core material may comprise layers ofmaterial with varying light propagation speeds, which may drasticallyalter the physical profile of the CRTR core, while maintaining thedesired taper with respect to wave propagation therein.

In one particular embodiment, the stamp/cover comprises a lens, or isformed as a lens after production of the CRTR's. Such lens would serveto capture light and other radiant energy and bring it to focus at planeof the CRTR apertures, or an extension thereof. By way of example, FIG.12 depicts an embodiment where the stamp/cover is formed to act as alens, with an outer surface 1291, while having the CRTR cores 1271 beingformed on the opposite surface. The pits 1275 are formed on thesubstrate 1200, the stamp is aligned and inserted into the CRTR pits1275, and the space between the cores and the stratum is filled with thecladding material by one of the methods described above.

In some embodiments lens 1270 has planarization surface 2905 andelectrical interconnects 2925 connecting to electrical connections 2930on substrate or die 1200. Optional encapsulant or package body (notshown) completes an electronic package for the device. The lens may forma portion of a larger optical system.

Thus, in certain embodiments, there is provided an array comprising aplurality of CRTRs which may be operated as splitters, combiners,reflective, or hybrid CRTRs. The array comprising a stratum having aplurality of pits formed therein, the pits being defined by pit walls,at least some of the pits being dimensioned to receive therein at leasta portion of the core and cladding of a CRTR. A cover transmissive ofradiant energy within a spectral range of interest of the device, has aplurality of protrusions extending therefrom, at least one of theprotrusions being dimensioned to act as the core of at least one of theplurality of CRTRs, is disposed in registration with a pit. A claddingis disposed between the protrusion and at least one of the walls of therespective pit, such that the protrusion acts as a core to the CRTformed in combination with the cladding.

Generally, in the creation of CRTRs, for the cladding, core, andintermediate material if one is used, it is permissible to use air,inert gas, or a cooling liquid of controlled dielectric constant andsufficiently low optical absorbance. Perfluoropolyether and fluoroalkaneliquids have very reproducible properties, excellent opticaltransparency, low viscosity and good wetting to hydrophobic metals.Mixtures of related fluids may be used to tune the dielectric constantin operation. These materials have excellent heat transfer propertiesand could be used to remove excess heat by flowing in the z-directionalong defined ridges if the etched regions form long slots.

Both low-k and high-k solid dielectrics are also suitable to the metalclad system; dielectric cladding favors low-k solids such as aluminumoxide, silicon dioxide, or polymers for the cladding and high-ktransparent materials for the core. Water and other aqueous liquidsallow the same fluid cooled system while using an alcohol/water or othersuitable mixture to continuously adjust the dielectric constant of thecore. Hafnium oxide is a well-known high-k material from thesemiconductor industry.

With respect to the CRTR, the term “tip” denotes the end opposite theaperture, which is commonly the narrow end of the CRTR core. The tip maybe flat, tapered to a point, rounded, cylindrical, or having any desiredshape. The tip may even extend to a broad end, after narrowing down. Insuch case the tip is considered the narrowest point in the waveguide.

Lately, stereoscopic displays appear in many devices. Such displaysprovide an illusion of three dimensional objects and are colloquiallyknown as “3D displays”, or 3 dimensional displays. It is noted thatthose devices are not truly three dimensional, but create the threedimensional illusion at the viewer's brain. The skilled in the art wouldrecognize that the CRTRs in general, and most specifically CRTRs actingas mixers, will offer significant advantages to regular displays as wellas to three dimensional displays. For two dimensional displays the CRTRoffer unique advantages in the field of micro displays, such as wearabledisplays and the like. For stereoscopic displays the CRTR offers theadvantage of allowing two separate signals to be emitted, each with itsown polarization. A plurality of CRTRs operating in mixer mode, incombinations with respective plurality of controllable light sourceswill create a display. If the light sources are disposed to providepolarization information a 3D display is formed. 3D display of this typewill be very compact and present multiple advantage over the presentcomplex construction. In both 2D and 3D embodiments, the display willprovide high efficiency and very small pixel size. Furthermore, thestacked nature of the lateral guides offers simplified wiring as thespace between the lateral waveguides may be utilized for wiring eachindividual layer.

As different embodiments of the present invention is applicable to manyroles, applications, and functions, and as the structures at the base ofthe invention cover a broad spectrum of electromagnetic radiation, it isrecognized that different disciplines often use different terms foritems that would represent similar concepts in differing fields. Thisbroad applicability points for a need to use words that depart somewhatfrom the strict common usage in a specific field, yet such terms areeither be well defined in the specifications, or will be clear to theskilled in the art by analogy, and in light of the teachings providedhereinabove. By way of example these specifications uses terms such aselectromagnetic radiation and radiant energy interchangeably. Similarly,the term ‘refractor’ and ‘splitter’ or ‘spectral splitter’ will be usedinterchangeably, as well as ‘mixer’ and ‘combiner’. Certain expressions,such as for example the term ‘refractor’ denotes a device which impartsan angle change to radiant energy, regardless of specific mechanisms,whether they relate to light or to any other part of the spectrum, andregardless of the specific mechanism utilized to impart that anglechange. The term ‘polychromatic’, ‘multi-frequency’ and ‘mixedfrequency’ are also be used interchangeably, and denote anelectromagnetic energy which comprises a plurality of spectralcomponents. The electromagnetic energy components may be spectralcomponents, i.e., components of different frequencies. Alternatively oradditionally, the electromagnetic wave components may be of differentpolarizations, whether or not of differing frequencies. Notably, theterms extend throughout the spectral range of interest.

A basic building block of most embodiments of the present inventioninvolves a waveguide having a tapered core. The terms ‘tapered corewaveguide’ and ‘tapered waveguide’ are used interchangeably. While thewaveguide including the cladding may be tapered, the requirement forthat building block is for the at least the core to be tapered.Furthermore, the term “tapering” and “taper” should be construed thatthe taper may have different widths at different locations, or stateddifferently, that the width of the core in at least one direction,changes as a function of depth. The term taper denotes more than a purelinear taper, i.e. a straight line connecting two points on the base andtip as seen in a cone. For example, in some embodiments, the core widthmonotonically decreases as one proceeds from a wider base to a narrowertip, while in other embodiments other functions may be utilized such asstepped function, logarithmic function, or any other desired function.Furthermore, the width may vary to different extent within a singledepth, as seen for example in the cores depicted in FIG. 8. The termsubstantially implies that the associated condition or limitation isfulfilled within tolerances which permit operation as described. By wayof example, while a certain component may be described as transverse, orbeing at 90 degrees to another, the skilled in the art would recognizethat certain tolerance exists and that as long as the purpose of thelimitation is served within such tolerance, the component or limitationis considered fulfilled.

Note, however, that use of the foregoing and similar terms of art shouldnot be construed as necessarily limiting all embodiments to modes ofoperation suggested by the strict technical senses of the termsemployed. The novel nature of the invention necessitate certainlexicographical freedoms to describe a structure and limitations. Theskilled in the art would readily recognize the proper application ofthese specifications when taken as a whole, and in light of commonknowledge and the state of the art. Various modes of the invention willbecome apparent in light of these specifications, and all suchvariations in which these terms are used should be considered within thescope of the invention.

It will be appreciated that the invention is not limited to what hasbeen described hereinabove merely by way of example. While there havebeen described what are at present considered to be the preferredembodiments of this invention, it will be obvious to those skilled inthe art that various other embodiments, changes, and modifications maybe made therein without departing from the spirit or scope of thisinvention and that it is, therefore, aimed to cover all such changes andmodifications as fall within the true spirit and scope of the invention,for which letters patent is applied.

What is claimed is:
 1. radiant energy conversion assembly comprising: astratum having a top and bottom surfaces and comprising a plurality ofsuperposed waveguides, at least one of the plurality of waveguideshaving at least a first transducer disposed therein; a tapered corewaveguide disposed at least partially within the stratum, the taperedcore waveguide comprising a hollow core having a first end and a secondend, the first end defining an aperture, the core having a depthdirection extending between the first end and the second end, andsubstantially perpendicular to the stratum top surface, wherein thedepth magnitude increases with distance from the first end towards thesecond end, and from the top surface towards the bottom surface of thestratum; the core being tapered and having a width magnitude at eachdepth such that the width magnitude at the aperture is higher than thewidth magnitude at the second end; a cladding disposed at leastpartially around the core; wherein the first end of the core isdimensioned to allow passage of at least a first and a second spectralcomponents having frequencies associated therewith, and wherein the coreis dimensioned such that first spectral component would reach a claddingpenetration state at a first location and the second spectral componentwill reach a cladding penetration state at a second location, differentfrom the first location.
 2. An assembly as claimed in claim 1, whereinthe tapered core is asymmetric, or having symmetrically multifacetedcross-section in at least one width plane substantially orthogonal tothe depth direction; and, the first location and the second locationform an angle therebetween when projected to at the width plane.
 3. Anassembly as claimed in claim 1, wherein the at least one transducer is areflective transducer disposed in the at least one superposed waveguideto controllably reflect at least a portion of the first spectralcomponents via the cladding into the core.
 4. An assembly as claimed inclaim 1, further comprising at least a first and a second radiant energysources disposed within at least one of the plurality of superposedwaveguides, to couple energy emitted from the energy sources to the corevia the cladding.
 5. An assembly as claimed in claim 1, wherein thetapered core is asymmetric, or having symmetrically multifacetedcross-section, at a width plane substantially orthogonal to the depthdirection.
 6. An assembly as claimed in claim 1, wherein at least one ofthe superposed waveguides having an electrically conductive cladding. 7.An assembly as claimed in claim 1, wherein the aperture is constructedas an elongated wedge.
 8. An assembly as claimed in claim 1, wherein thefirst and second spectral components each having a different frequencyassociated therewith, at least two of the superposed waveguides aredisposed to receive the first and second spectral componentsrespectively, and each of the at least two superposed waveguides havinga transducer disposed therein, the respective transducer optimized forthe frequency of the spectral component received by the respectivewaveguide.
 9. An assembly as claimed in claim 1, wherein the first andsecond spectral components each having a different frequency associatedtherewith, at least two of the superposed waveguides are disposed toreceive the first and second spectral components respectively, and eachof the at least two superposed waveguides having a thickness optimizedfor the frequency of the spectral component received by the respectivewaveguide.
 10. An assembly as claimed in claim 9, wherein the thicknessof at least one of of the least two superposed waveguides is between onewavelength and a half wavelength of the respective spectral component.11. an assembly as claimed in claim 1, wherein the cladding of thetapered waveguide comprises metal having a thickness in the order of, orlower than, the skin penetration depth for at least one spectralcomponent admitted via the aperture, at or about the claddingpenetration depth of the spectral component.
 12. An assembly as claimedin claim 1, further comprising a plurality of tapered core waveguidesdisposed at least partially in the stratum.
 13. An assembly as claimedin claim 1, wherein the stratum top surface comprises metal.
 14. Anassembly as claimed in claim 1, wherein the first the frequencyassociated with the first spectral component is lower than the frequencyassociated by the second spectral component, the first location is at alower depth than the second location, and wherein at least two of theplurality of superposed waveguides are disposed to receive the first andsecond spectral components respectively.